1. Field of the Invention
This invention relates to a solid fuel which at least partially includes a recycled residue from anaerobic fermentation of an organic material.
2. Description of Prior Art
Municipal Solid Waste (MSW) can be processed into a Refuse Derived Fuel (RDF). The RDF can be used either alone or with coal as a solid fuel. The RDF and coal combination solid fuel has been co-fired with or densified into pellets. However, such RDF and coal combination solid fuel does not have a very high heat content, relative to coal alone, and has high ash content. For example, most RDF has a heat content of 5,000 to 8,000 Btu/lb dry matter and requires a non-voltage binder when densified, or compressed, into a solid fuel.
When burned, such REF and coal combination solid fuels produce combustion products with a high content of sulfur oxides (SO.sub.x), particularly sulfur dioxide (SO.sub.2), nitrogen oxides (NO.sub.x), total hydrocarbons (THC) and ash. As the heat content of the RDF and coal combination solid fuel increases, the cost of further processing and densifying the RDF and coal combination also increases. With pure coal or a combination solid fuel of coal and RDF as a fuel, power plants typically will operate with relatively high SO.sub.2, NO.sub.x and THC emissions, with respect to Environmental Protection Agency (EPA) standards, and if such fuels are burned, then many existing power plants require costly retrofits or equipment modifications in order to meet EPA standards. Particularly in the Midwestern United States, such emissions are extremely high due to the high-sulfur content coal readily available to and often used within such power plants. Under current EPA standards, power plants are required to operate with Best Available Control Technology (BACT) which includes stack emissions control devices, such as scrubbers and bag houses.
There exists a need for a solid fuel and process for combustion of a solid fuel wherein undesirable emissions such as SO.sub.2, NO.sub.x and THC are reduced to meet EPA emissions standards without the need for additional and expensive equipment modifications, heat content values are increased and costs, particularly those costs associated with burning coal, are reduced.